A study of the impacts of vertical diffusion on the structure and intensity of the tropical cyclones using the high-resolution HWRF system

Sundararaman G. Gopalakrishnan, Frank Marks, Jun A. Zhang, Xuejin Zhang, Jian Wen Bao, Vijay Tallapragada

Research output: Contribution to journalArticlepeer-review

112 Scopus citations

Abstract

The Hurricane Weather Research and Forecasting (HWRF) system was used in an idealized framework to gain a fundamental understanding of the variability in tropical cyclone (TC) structure and intensity prediction that may arise due to vertical diffusion. The modeling system uses the Medium-Range Forecast parameterization scheme. Flight-level data collected by a NOAAWP-3D research aircraft during the eyewall penetration of category 5HurricaneHugo (1989) at an altitude of about 450-500 mandHurricaneAllen (1980)were used as the basis to best match the modeled eddy diffusivitieswith wind speed.While reduction of the eddy diffusivity to a quarter of its original value produced the best match with the observations, such a reduction revealed a significant decrease in the height of the inflow layer as well which, in turn, drastically affected the size and intensity changes in themodeled TC. The cross-isobaric flow(inflow)was observed to be stronger with the decrease in the inflow depth. Stronger inflow not only increased the spin of the storm, enhancing the generalized Coriolis term in the equations of motion for tangential velocity, but also resulted in enhanced equivalent potential temperature in the boundary layer, a stronger and warmer core, and, subsequently, a stronger storm.More importantly, rapid acceleration of the inflow not only produced a stronger outflow at the top of the inflow layer, more consistent with observations, but also a smaller inner core that was less than half the size of the original

Original languageEnglish (US)
Pages (from-to)524-541
Number of pages18
JournalJournal of the Atmospheric Sciences
Volume70
Issue number2
DOIs
StatePublished - Feb 2013

Keywords

  • Mesoscale models
  • Parameterization
  • Regional models
  • Tropical cyclones

ASJC Scopus subject areas

  • Atmospheric Science

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